Get the TOTAL CONTROL book by Lee Parks. It's great. Everyone so far has given pretty sound advice. What I've learned about getting that knee down is that it's NOT about speed, but it's far more about body position.
Here I was at about 20mph on Pilot Road tires (Taking the TC course with Lee Parks):
Body position is everything, especially on the Monster. Remember to turn your shoulders in the direction of your turn, a lot of riders forget that crucial move. If you are in the correct position say for a left bank turn, you should notice that:
1) Your right elbow is against the right side of the tank (or very close) but relaxed.
2) The right side of your chest is against the tank (or very close to it).
3) Your left wrist should feel taught the weight of your body falling gradually over towards your left arm.
4) Your right leg is wide (but snug) on the tank, but firmly squeezing your right foot and heel into the foot grip.
5) Your shoulders are twisted in the direction of the turn.
6) Your head is focused on looking THROUGH the turn.
7) Your derrier is far to the left, your left leg is out in a natural leaned position.
8 ) You are RELAXED - you have to breath. Taking a deep breath before you initiate this process is VERY helpful to get your body down in the right position.
Just look at Lee's body position:
and again:
I don't think that I've forgotten anything, but really, reading the TC book will really help you conceptialize this process.
Oh, one more thing, don't
EVER try and ride on the road as though you were on the track.